Temperature-Induced Morphological Transitions of Poly(dimethylacrylamide)–Poly(diacetone acrylamide) Block Copolymer Lamellae Synthesized via Aqueous Polymerization-Induced Self-Assembly

Aqueous dispersion polymerization of diacetone acrylamide (DAAM) by chain extension from a hydrophilic poly(N,N-dimethylacrylamide) (PDMA30) macromolecular chain transfer agent (macro-CTA) to produce PDMA30–PDAAMx block copolymer nano-objects was investigated in detail by systematically varying solids content and degree of polymerization of the core-forming PDAAM, leading to the formation of pure lamellae, mixed lamellae/vesicles, and pure vesicles as revealed by dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM). PDMA30–PDAAMx lamellae were found to span an unprecedented wide space in the morphology phase diagram. Moreover, in situ cross-linking of lamellae via statistical copolymerization of DAAM with an asymmetric cross-linker allyl acrylamide and the effect of cross-linking density on the colloidal and morphological stabilities were studied, representing the first report on in situ cross-linking of lamellae during polymerization-induced self-assembly (PISA). Finally, reversible, temperature-induced morphological transitions from lamellae to worms/spheres on cooling were investigated by DLS, TEM, 1H NMR spectroscopy, and rheology. The kinetics of the temperature-dependent morphological transitions and the rheological properties could be tuned by the cross-linking density.